The following extract comes from The Yoga Sutras of Patanjali, Book One - Samadhi Pada (Portion on Contemplation);
"Why does a candle burn and melt away? To give light. Why does am incense stick burn to ash? To give fragrance. Why does a tree grow? To give fruit and flowers. Is there anything, sentient or insentient, in this world that lives for it's own sake? No. When the entire nature sacrifices, why should we human beings along lead selfish lives? We are here to give and give and give. What is due to us will come without our worrying about it.
Of course, even here we might wonder, "If I am to lead a sacrificial life, how can I eat, how can I clothe myself or have a house of my own?"
You can have all these things to equip yourself to serve others.
You must have a bed to rest in to feel refreshed in the morning, in order to go out to serve others. You must eat to have enough energy to serve others. So you do everything with the idea that you are preparing yourself to serve others. Even the practice of meditation is not done just for your own peace but it is done because with a peaceful mind you can go out into the world and serve well."